Foot boring machine for dentists with driving motor



Dec. 1 1925.

P. FRANKE FOOT BORING MACHINE FOR DENTISTS WITH DRIVING MOTOR Filed Nov. 25. 1924 Patented Dec. 1, 1925.

U S'i"ia"r PAUL FRANKIE, OF BERLIN, GERMANY.

FOOT BORING MACHINE FOR DENTISTS W'ITH DRIVING- MOTOR.

Application filed November To all whom it may concern:

Be it known that I, PAUL FRANKE, a citizen of the German Republic, residing at Berlin, Germany, have invented certain new and useful Improvements in Foot Boring Machines for Dentists with Driving Motors, of which the following is a specification.

In foot boring machines for dentists with driving motor the motor has been hitherto clamped on the vertical shaft of the machine so that it can rotate with this vertical shaft. According to the invention the manner of fixing the motor overcomes the inconvenience that the motor is situated at the side of the vertical shaft so that its weight acts on a comparatively long lever arm with regard to the vertical shaft and that the oscillations of the motor are evidently transmitted to this shaft.

According to the invention the vertical shaft, or a part of the same, is of such shape that the centre of gravity of the motor can be laid into the axis of the vertical shaft so that the strain exerted by the motor on the shaft is always uniform and no vibrations can occur in the system.

An embodiment of the invention is illustrated, by way of example, on the acconr' panying drawings in which Fig. 1 shows in elevation the upper part of the vertical shaft with motor.

Figs. 2 to Al illustrate diagrammatically several forms of the part of the vertical shaft designed to accommodate the motor.

Figs. 5 and 6 illustrate diagrammatically two other forms of the part of the vertical shaft for accommodating the motor.

Fig. 7 shows a complete foot boring machine with driving motor constructed in accordance with the invention.

As can be seen from Figs. 1 and 7 the top part of the vertical shaft B of the boring machine A is composed of two parts between which a U-shaped bow consisting of the parts a, 'r, b, o", and c, is inserted. The vertical ends I), 0 of the tlshaped bow are preferably extended at the lower and upper end. The extension of the upper arm I) is hollow and a bolt is controlled by a spring 0 is located in the same. The motor 6 is mounted between the bolt a, which has at its lower end a rubber part on, and a rubber pad Z on the extension of the lower arm 0 of the li -shaped bow. In the upper end of the vertical arm Z) of the U-shaped bow a bore 25. 1924. Serial No. 752,269.

b is arranged designed to receive the end (Z of the support (Z for the driven shaft. From the lower end of the vertical arm 0 of the U-shaped bow projects a pin 0' designed to be inserted into a corresponding bore in the lower part of the vertical shaft 13.

The U-shaped bow may be made from round or flat iron, metal tubing or the like and it may be of different shapes as will be hereinafter described.

As shown in Fig. 2 the bow is reinforced by a diagonal stay g so that the motor can be clamped very steadily. An even greater security can be obtained when the parallel horizontal arms 1 1" (Fig. 3) of the bow are upwardly inclined and reinforced by horizontal stays g. A double or closed bow 8 may be used as shown in Fig. l.

When the motor has to be subsequently mounted on a foot boring machine A of standard type one has to count with a comparatlvely short axial distance a of the driven disk 7 from the driven shaft. In this case the motor is mounted between the two parts of the vertical shaft by means of an elastic metal band a placed, as shown in Flg. 5, around the cylindrical part j of the actor i, a strip 25 of felt being preferably inserted between the metal band and the 1notor, and a stretcher ois used for connecting the ends of the metal band. The metal band a must form a rigid system with the two vertical pins 1), c. In this case the centre of gravity is situated slightly at the side of the axis of the vertical shaft, but the oscillations of the motor and of the vertical shaft are considerably. less great than if the motor were fixed on the vertical shaft by clamps, the distance between the motor and the vertical shaft being much shorter.

The U-shaped bow may further be constructed like a yielding joint as shown in Fig. 6. The metal band which tightly encircles the motor casing is enclosed by a circular envelope y in which it can oscillate as indicated by the double arrow. In order that the bow returns, after any movement, into its initial position a downwardly projecting arm to is mounted between spring 2 in the cylindrical extension 2 of the envelope y.

The bow might further form a ball-joint.

The motor casing itself might further be constructed to serve as bow. With this object in view the motor casing must have two studs or sleeves situated in alignment on which the vertical shaft of the n'iacliine and the support (Z are to he fixed.

I claim l. A motor driven loot boring machine for dentists comprising in combination with the Vertical shaft of the machine composed of two separate parts, a U-shaped bow inserted between said two parts of the vertical shaft and means for securely mounting the motor in said how so that its centre of gravity is situated in the axis o t the vertical shaft.

2. A motor driven :loot boring machine for dentists comprising in conibination with the 'ertical :r-shalt ot the machine composed of two separate parts, a U-shaped how inserted between said two parts of the vertical shaft, a motor and an elastically mounted pin on one of the vertical arms of said how for securely mounting said motor in said bow so that its centre 0t gravity is situated in the axis 01 the vertical shaft.

in testimony whereof I am my signature.

PAUL FRANKE. 

